Mesh goes dark blue after applying auto smooth, happens when i flip normals
You don't need to Flip Normal Directions, you can just adjust Offset in Solidify modifier tab. This method will allow you too choose which side you want to "extrude" or you can even have it in the middle (0 value).

Also you can check Flip Normals in Solidify modifier options, if you by mistake have flipped normals - this one will help you to make them right.